One example of conventional dust collectors is disclosed in Japanese Patent Unexamined Publication No. 2004-53079 using a spiral case and multiblade fans whose diameter is as large as 50% or more of the length of the short side of the body. In this type of dust collector, the thickness in the shaft direction is usually about 15% of the fan diameter.
The conventional dust collector is described as follows with reference to drawings. FIG. 4 is a sectional side view of the conventional dust collector. As shown in FIG. 4, the dust collector includes impeller 101 having spiral case 102. Impeller 101 has diameter 103, which is at least half of the length of short side 105 of body 104, and thickness 106 in the shaft direction, which is about 15% of diameter 103. The dust collector further includes dust collecting filter 107 disposed on the inlet side.
Such conventional dust collectors have a large thickness. Therefore, the inlet space should be small when the dust collectors are designed for use in clean rooms or integrated into devices that are required to be kept clean. This causes a large air pressure loss, and as a result, an increase in the air flow of the dust collector causes an increase in power consumption and noise.